Method of grease manufacture



April 5, 198 w. R. HENCKE ETAL 3,244,628

METHOD OF GREASE MANUFACTURE Filed May 22, 1963 United States Patent3,244,628 METHOD OF GREASE MANUFACTURE William R. Henclke, Groves,William R. Coons, .lr., and

(Ilarence L. Dowden, Jr., Port Arthur, and William R.

Green, .l'r., Groves, Tex., assignors to Texaco 1110., New

York, N .Y., a corporation of Delaware Filed May 22, 1963, Ser. No.282,339 Claims. (Cl. 252-39) This invention relates to an improved lowtemperature method for the preparation of soap thickened greases. Itrelates particularly to an improved low temperature method for thepreparation of greases thickened with lithium or calcium soaps ofhydroxy fatty acids.

Copending application Serial No. 282,330, filed of even date herewith byL. F. Badgett, W. R. Hencke and F. T. Crookshank, discloses and claimsan improved low temperature method of grease manufacture which involvescontinuously recirculating the grease mixture from a grease making zonethrough a recycle line with injection of additional oil at a lowertemperature into the recirculating stream of grease mixture during thecooling cycle, and preferably with injection of preheated oil during theheating cycle also. By this method, large reductions in themanufacturing times as well as increased yields are obtained.

We have found, in accordance with the present invention, that additionaladvantages are unexpectedly obtained in carrying out the preparation ofsoap thickened greases by the above procedure by employing a lowtemperature holding step following the saponification step in place ofor in addition to a holding step at the top temperature, asconventionally employed in low temperature grease preparations. The lowtemperature holding step is carried out following the saponification andsubstantial dehydration by holding the grease mixture for a minimumperiod of about minutes, and preferably for at least about 30 minutes,within the temperature range from about 200 F. to about 240 F. withcontinuous recirculation through a recycle line. In some cases,particularly in the preparation of greases which are difiicult toprepare in satisfactorily smooth form, such as lithium and calciumhydroxy fatty acid soap thickened greases, the grease mixture ispreferably subjected to continuous shearing during the low temperatureholding step, suitably by means of a shear valve in the recycle lineoperated with at least a substantial pressure drop across the valve.

By carrying out the preparation of soap thickened greases by the recycleprocedure of Badgett et al. with a low temperature holding step asdescribed above, improved yields and product quality are obtainedwithout substantially increasing the manufacturing time, and in somecases even with reduced manufacturing times. The method of thisinvention is employed with special advantage in the preparation ofcalcium and lithium hydroxy fatty acid soap thickened greases andparticularly in the preparation of such greases containing parafiinicoils as the oil component.

While the reason for the effect of the low temperature holding step inthe recycle procedure is not entirely understood, it is known that therecycling has a marked effect upon the soap fiber development, resultingin longer and more dispersed fibers, and it is thought that the effectof the low temperature holding step is due to decreasing the rate offiber growth which permits an increased etfect of the recycling upon thecharacter of the fibers. In the case of greases which tend to form roughor grainy products, shearing during this step prevents the formation ofaggregates which are difficult or impossible to redisperse at laterstages in the grease making process.

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The figure is a diagrammatic illustration of a particularly suitableapparatus for making greases in accordance wit-h this invention.

Referring in more detail to the figure, numeral 1 represents a jacketedgrease kettle equipped with stirrer 2 and adapted to be heated toelevated temperatures above about 350 F. In carrying out the greasepreparation, the grease kettle is charged with saponifiable material,lubricating oil and metal base in approximately the stoichiometricamount required to react with the saponifiable material. Water may beadded to the charge also, suitably in an amount equal to from about 0.5to about 10 times the weight of the metal base, although this is usuallynot required in the preparation of calcium hydroxy fatty acid soapthickened greases and the preparation of lithium hydroxy fatty acid soapthickened greases may be carried out without added water when employingrecycling at high recycle rates. The lubricating oil and saponifiablematerial may be employed in a weight ratio between about 1:2 to about6:1, respectively, and preferably in a weight ratio from about 1:1 toabout 5:1, respectively. The kettle contents are heated in the kettlewith stirring until the saponification is complete and the mixturesubstantially dehydrated and then further heated with recirculation ofthe resulting grease mixture. Re circulation from the bottom to the topof kettle 1 is begun by turning valves 6 and 8 to the open position andstarting pump 12. The grease mixture passes through line 5 containingvalve 6, line 10 containing valve 8, pump 12, line 14 containingpressure gauge 15 and shear valve 19, which is suitably a gate valve,and is returned at the top of kettle 1 as shown in the diagram. Thecirculation is ordinarily begun following the saponification andsubstantial dehydration and continued throughout the remainder of theprocess. However, it may be carried out during the saponification also,if desired, to obtain increased mixing of the reactants.

Following the saponification and substantial dehydration, the greasemixture is heated to a temperature in the range from about 200 F. toabout 240 F., and maintained at a temperature in this range from about15 minutes to about 1 hour. The preferred temperature range variessomewhat for different greases, depending principally upon the characterof the soap thickener, a temperature range for this step of aboutZOO-235 F. being generally optimum for calcium soap thickened greasesand a temperature range of about 220240 F. being generally optimum forlithium soap thickened greases. Recirculation of the grease mixturethrough the recycle line in the manner described above is carried outcontinuously during this holding period at a rate such that the weightof recirculated grease mixture equals the total weight of greasemixture, i.e. one batch turnover, in from about 0.25 to about 15minutes, preferably in from about 0.25 to about 10 minutes, andordinarily in from about 0.25 to about 5 minutes.

Recirculation of the grease mixture during the low temperature holdingstep is very advantageously carried out in some cases with valve 19 in apartly closed position, so as to give a pressure drop of about 10 to 200pounds per square inch across the valve, and preferably with a pressuredrop of about 25 to pounds per square inch across the valve. Thepreferred procedure comprises shearing in this manner during the holdingstep carried out for a suflicient period and with recycle ratesproviding at least 5 batch turnovers, and preferably at least 10 batchturnovers during this heating period. Recirculation with shearing of thegrease mixture in this manner may also be carried out at later stages ofthe grease making process if desired.

Following the low temperature holding step, the grease mixture is heatedto a temperature in the range from just below the melting point of thesoap to about 75 F. below the melting point of the soap with continuedrecirculation of the grease mixture. The heating may be accomplishedrapidly by introducing preheated oil into the recirculating stream ofgrease mixture. The oil added in this manner passes from tank to heater30 by way of line 22 containing valve 23, pump 24, line 25 and line 28containing valve 29. Heater 30 may be a heater of any suitable type suchas a coil heater as indicated in the diagram. From heater 30 the oilpasses into line 26, containing valve 27, dial thermometer 33, pressuregauge 34 and valve 35. Valve 35 is preferably a one-way valve, mostsuitably of a type designed to prevent gravity flow of oil through pump24 when the pump is not operating, such as a diaphragm controlledreducing valve or a spring loaded check valve. From line 26 the oilpasses into line 36 and may be introduced into the recirculating streamof grease mixture at the intake side of pump 12 by passing through valve37 into line 10, or at the discharge side of pump 12 by passing throughvalve 38 into line 14. duced at the intake of pump 12 in order to obtainincreased mixing by the action of the pump, except where a light oil isemployed which may cause vapor locking of the pump. The oil added inthis manner is ordinarily at a temperature substantially higher thanthat of the grease mixture and may be up to or even slightly higher thanthe melting point of the soap. This oil may be introduced into therecirculating stream of grease mixture at a rate such that the ratio ofthe rate of flow of the grease mixture before the point of confluence tothe rate of oil injection is from about 1:1 to about 400:1, preferablyin a ratio from about 2:1 to about 150:1, and most advantageously in aratio from about 3:1 to about 50:1, by Weight, respectively. The amountof oil added in this manner may be from about 5 percent up to about 70percent of the total oil contained in the finished grease. In thepreparation of lithium hydroxy fatty acid soap thickened greases it ispreferably not above about 50 percent, and most suitably from about 10to about 30 percent by weight of the total oil employed in the grease.

Circulation of the grease mixture through the recycle system during theheating cycle following the low temperature holding step is carried outat a rate sufficient to give one batch turnover within about 22 minutes,such as in about 0.3-22 minutes, and preferably in about 04-15 minutes,based on the Weight of the grease mixture during the heating cycle, orin about 0.25-10 minutes, and preferably 0.3-12 minutes based upon theaverage weight of grease mixture during the heating cycle when theprocess is carried out with additional oil added during the heating stepas described hereinbelow. The use of a low temperature holding step inaccordance with this invention is particularly advantageous as a meansof obtaining the desired yields and product quality in the processcarried out with relatively low recycle rates during the heating step,such as those requiring at least about 5 minutes for a batch turnover.Recycling during the cooling cycle is suitably carried out at a ratesufficient to provide a batch turnover in about 0.535 minutes, andpreferably in about 1-20 minutes, based on the weight of the finishedgrease, or in about 04-27 minutes, and preferably about 0.5-17 minutes,based on the average weight of grease mixture during the cooling cycle.

In some cases, it is desirable to employ a high temperature holding stepin addition to the low temperature holding step described above. Such astep is carried out by maintaining the grease mixture at a temperaturein the range from just below the melting point of the soap down to about75 F. below the melting point of the soap for a period from about 15minutes to 1 hour, or longer if It is preferably intro-,

desired. It is preferably carried out at a temperature in the range fromjust below the melting point of the soap down to about 50 F below themelting point of the soap. The total heating time from the end of thesaponification step to the beginning of the cooling step will ordinarilybe in the range from about /2 hour to about 4 hours, and under thepreferred conditions, in the range from about 1 to 3 hours.

Cooling of the grease mixture is carried out with the introduction oflubricating oil at a relatively low temperature, such as at least aboutF. and preferably at least about F. below the temperature of the greasemixture at the beginning of the cooling step, into the recirculatingstream of grease mixture. The lubricating oil passes from tank 20 intoline 36 by way of line 22, pump 24, line 25 and line 26, bypassingheater 30. In line 36, the lubricating oil may pass through valve 37into the stream of grease mixture at the inlet side of pump 12 orthrough valve 38 into the stream in the discharge side of pump 12 asdescribed above in connection with the introduction of preheated oil.The oil addition is preferably commenced at the beginning of the coolingstep, and may be carried out over the entire cooling period or duringonly a portion thereof. Additional cooling may be applied to the kettle,and also to the recirculating stream of grease mixture. The lubricatingoil added during the cooling may amount to from about 10 to as high asabout 90 percent of the total oil contained in the grease. It willusually be from about 25 to about 75 percent of the total oil containedin the grease. The rate of oil addition may suitably be such that theratio of the rate of recirculation of the grease mixture to the rate ofoil injection is within the ranges disclosed hereinabove in connectionwith the injection of preheated oil during the heating cycle. When theoil addition is carried out during only a portion of the cooling step itis advantageous in some cases to continue recirculation of the greasemixture with shearing down to the drawing temperature. Additives may beadded to the grease mixture when it has been cooled to a suitably lowtemperature, ordinarily at below about 250 F. The grease mixture isfinally drawn from the kettle through line 40 containing valve 41.

The metal base employed in the saponification may be a hydroxide orother suitable compound of any of the metals ordinarily employed as themetal component of soaps in grease making, such as sodium, lithium,potassium, calcium, barium, magnesium, zinc, cobalt, manganese,aluminum, lead, etc. as well as mixtures of two or more metals. It ispreferably a metal oxide, hydroxide or carbonate. The greases which aremost advantageously prepared by the method of this invention are thosewherein the soap thickener is an alkali metal or alkaline earth metalsoap, or a mitxure of two or more soaps of this class.

Saponifiable materials which may be employed in the grease preparationcomprise higher fatty acids and hydroxy substituted fatty acidscontaining from about 12 to 32 carbon atoms per molecule and theglycerides and other esters of such acids. The preferred materials arefatty acids and hydroxy fatty acids containing about 14 to 22 carbonatoms per molecule, their glycerides and other esters, and mixtures ofsuch materials.

The oleaginous liquids employed in these greases may be any oils oflubricating characteristics suitable for use in grease making generally,including the conventional mineral oils, synthetic oils obtained byvarious refining processes, such as cracking and polymerization, andother synthetic oleaginous compounds, such as high molecular weightethers and esters. The dicarboxylic acid esters, such as di-Z-ethylhexylsebacate, di(secondary amyl) sebacate, di-Z-ethylhexyl azelate,di-iso-octyl adipate, etc, are a particularly suitable class ofsynthetic oils and may be employed as the sole oleaginous component ofthe grease or in combination with other synthetic oils or mineral oils.The oil employed in the initial charge is preferably one which issubstantially inert under the saponification conditions, such as amineral oil. Suitable mineral oils for use in these greases are thosehaving viscosities in the range from about 100 to about 2,000 secondsSaybolt Universal at 100 F. and may be either naphthenic or paraflinicin type or blends of the two.

The following example is illustrative of grease preparations carried outin accordance with the preferred embodiment of this invention.

EXAMPLE I A lubricating grease comprising a mineral lubricating oilthickened with calcium 12-hydroxysteara te was prepared by the method ofthis invention as described below.

The following materials were employed in this preparation: The mineraloil employed was a refined paraffinic distillate oil having a SayboltUniversal viscosity at 100 F. of 346 seconds, with about 1 percent byweight of a heavy parafiinic residual oil having a Saybolt Universalviscosity at.210 F. of 658 seconds. The saponifiable material employedwas a commercial 12-hydroxystearic acid having a neutralization numberof 173, a saponification number of 187 and an iodine number of 6.

The equipment employed comprised a 150 pound capacity steam heatedkettle with auxiliary equipment for grease circulation with hot and coldoil injection into the recycle stream as shown in FIG. 1. The greasecirculation equipment consisted of 1% inch pipe connecting the kettledrawofi' with a No. 2 Globe Rota Piston pump having a capacity of 18gallons per minute, and a inch pipe extending from the pump to the topof the kettle, containing a gate valve employed as a shear valve.

Following is a detailed description of the method employed in the greasepreparation: The kettle was charged with 27 pounds or" parafiinicdistillate oil, 1.25 pounds of lime and 9.0 pounds of 12-hydroxystearicacid. Heating and stirring of the kettle contents was begun and at thesame time recirculation of the kettle contents through the recycle linewas begun at a rate of about 120 pounds per minute with the shear valvein the wide open position. After about 15 minutes, the temperature ofthe reaction mass had reached 180 F. and saponification had started.After an additional 15 minutes with continued heating the temperature ofthe mass had reached 218 F. and dehydration was substantially completeas shown by the cessation of foaming. The heating was then continued ata slower rate sufiicient to maintain the reaction mass at 225-232 F. for/2 hour. Thereafter, the steam pressure was increased and thetemperature brought up to 264 F. in about 23 minutes while pounds of theparaffinic distillate oil preheated to 265-276 F. were added at a rateof about 120 pounds per hour into the recirculation line at the intakeside of the pump. When the temperature of the mixture had reached 240F., the shear valve was adjusted to give a pressure drop across thevalve of 60 pounds per square inch and recirculation with shearing inthis manner continued during the remainder of this process, amounting toa total time of about 1 hour and minutes. When the temperature of thegrease mixture was 270 F., the heat was cut off and cooling commencedwith the addition of 23 pounds of distillate oil at ambient temperatureat a rate of 120 pounds per hour during the cooling down to 234 F.,which required about 12 min utes. During further cooling of the greasemixture to 179 F., 0.53 pound of diphenylamine, 1.06 pounds of the heavyresidual oil and an additional 15 pounds of paraffinic distillate oilrequired for correction of the grease grade were added. The grease wasdrawn at 179 F.

A smooth grease of good yield and appearance was obtained as describedabove. The following table shows the eifect of the low temperatureholding period in this preparation.

6 T able I Grease No u 1 l 2 3 1 Soap particles.

The grease preparations shown in the above table were all carried out insubstantially the same manner except for the differences in the holdingstep shown in the table. As shown by these results, relatively pooryields and unsatisfactory products were obtained by the process carriedout in very short manufacturing times with no holding period or only aA. hour holding period at top temperature. However, smooth products andgood yields were obtained by employing a /2 hour low temperature holdingstep. By carrying out the preparation without a low temperature holdingstep but with a one hour holding period in the top temperature range,yields substantially equivalent to those shown above for Grease No. 3were obtained but the appearance of the grease was less satisfactory, inaddition to the disadvantage of the longer manufacturing time required.The advantage obtained by employing a low temperature holding step inthe preparation of this grease containing a naphthenic oil as the oilcomponent is ordinarily much less than that shown above for the greasecomprising a paraflinic oil. However at least a substantial advantage inyield or product quality is ordinarily obtained by means of the lowtemperature holding step even in the preparation of greases fromnaphthenic oils, particularly in the process employing relatively lowrecycle rates as discussed hereinabove, and the preparation of calciumbase greases comprising naphthenic oils is accordingly included withinthe purview of this invention.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. The process of preparing soap thickened greases which comprisesproviding a reaction mixture consisting essentially of a saponifiablematerial, a metal base in an amount corresponding approximately to thestoichiometric amount required to react with the said saponifiablematerial, a lubricating oil which is substantially unreactive under thesaponification conditions in an amount equal to about 0.5 to about 6times the weight of the said saponifiable material, heating the saidmixture up to about 200 F. over a period of time sufiicient to obtainsubstantially complete saponification, further heating the greasemixture up to a maximum temperature in the range from just below themelting point of the soap to about F. below the melting point of thesaid soap, and cooling with the addition of additional lubricating oilat a lower temperature than the grease mixture, said grease mixturebeing heated in the temperature range from 200 F. to the said maximumtemperature from about /2 hour to 4 hours, including about 15 minutes to1 hour at a temperature in the range from 200 F. to about 240 F. afterthe saponification step, said grease mixture being maintained in agrease making zone during the said grease making process withrecirculation through a recycle line at a rate such that the weight ofrecirculated grease mixture is equal to the total weight of greasemixture in about 0.25 to about 15 minutes during heating in the rangefrom 200 F. to 240 F., and with shearing of the grease mixture in thesaid recycle line during at least a substantial portion of the greasemaking process following the saponification step, said shearing beingcarried out by passing the recirculating mixture in said recycle linethrough a shear valve with a pressure drop across said valve of about10-200 pounds per square inch.

2. The process of claim 1 wherein the said cooling is carried out byintroducing additional oil at a substantially lower temperature into therecirculating stream of grease mixture.

3. The process of claim 1 wherein additional oil at a substantiallyhigher temperature than the grease mixture is introduced into therecirculating stream of grease mixture during the heating from about 240F. to the maximum temperature employed.

4. The process of claim 1 wherein the grease mixture is maintained at atemperature from just below the melting point of the soap to about 75 F.below the melting point of the soap for a period from about 15 minutesto about 1 hour.

5. The process of claim 1 wherein the recirculating stream of greasemixture is subjected to shearing during the cooling step by passing itthrough a shear valve with a pressure drop of about 10-200 pounds persquare inch across the valve.

6. The process of claim 1 wherein the grease mixture is subjected toshearing during the heating cycle by pass- 25 ing the recirculatingstream of grease mixture through a 8 shear valve with a pressure dropacross the valve of about 25-125 pounds per square inch.

7. The process of claim 1 wherein the said grease mix ture is subjectedto shearing during the cooling cycle and at least a portion of theheating cycle by passing it through a shear valve with a pressure dropacross the valve of about 25-125 pounds per square inch.

8. The process of claim 1 wherein the said soap is a calcium-hydroxyfatty acid soap.

9. The process of claim 1 wherein the said soap is a lithium-hydroxyfatty acid soap.

10. The process of claim 1 wherein the said lubricating oil is aparaflinic oil.

References Cited by the Examiner UNITED STATES PATENTS 2,450,220 9/1948Ashburn et al 25241 2,870,090 1/1959 Pitrnan et a1. 252-39 3,015,6241/1962 Hencke et a1 252-41 3,068,175 12/1962 Roach et a1. 25239'3,079,341 2/1963 Coons et al 25241 3,117,087 l/1964 McCormick et a1.2524l DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

1. THE PROCESS OF PREPARING SOAP THICKENED GREASES WHICH COMPRISESPROVIDING A REACTION MIXTURE CONSISTING ESSENTIALLY OF A SAPONIFIABLEMATERIAL, A METAL BASE IN AN AMOUNT CORRESPONDING APPROXIMATELY TO THESTOICHIOMETRIC AMOUNT REQUIRED TO REACT WITH THE SAID SAPONIFIABLEMATERIAL, A LUBRICATINGB OIL WHICH IS SUBSTANTIALLY UNREACTIVE UNDER THESAPONIFICATION CONDITIONS IN AN AMOUNT EQUAL TO ABOUT 0.5 TO ABOUT 6TIMES THE WEIGHT OF THE SAID SAPONIFIABLE MATERIAL, HEATING THE SAIDMIXTURE UP TO ABOUT 200*F. OVER A PERIOD OF TIME SUFFICIENT TO OBTAINSUBSTANTIALLY COMPLETE SAPONIFICATION, FURTHER HEATING THE GREASEMIXTURE UP TO A MAXIMUM TEMPERATURE IN THE RANGE FROM JUST BELOW THEMELTING POINT OF THE SOAP TO ABOUT 75*F. BELOW THE MELTING POINT OF THESAID SOAP, AND COOLING WITH THE ADDITION OF ADDITIONAL LUBRICATING OILAT A LOWER TEMPERATURE THAN THE GREASE MIXTURE, SAID GREASE MIXTUREBEING HEATED IN THE TEMPERATURE RANGE FROM 200*F. TO THE SAID MAXIMUMTEMPERATURE FROM ABOUT 1/2 HOUR TO 4 HOURS, INCLUDING ABOUT 15 MINUTESTO 1 HOUR AT A TEMPERATURE IN THE RANGE FROM 200*F. TO ABOUT 240*F.AFTER THE SAPONIFICATION STEP, SAID GREASE MIXTURE BEING MAINTAINED IN AGREASE MAKING ZONE DURING THE SAID GREASE MAKING PROCESS WITHRECIRCULATION THROUGH A RECYCLE LINE AT A RATE SUCH THAT THE WEIGHT OFRECIRCULATED GREASE MIXTURE IS EQUAL TO THE TOTAL WEIGHT OF GREASEMIXTURE IN ABOUT 0.25 TO ABOUT 15 MINUTES DURING HEATING IN THE RANGEFROM 200*F. TO 240*F. AND WITH SHEARING OF THE GREASE MIXTURE IN THESAID RECYCLE LINE DURING AT LEAST A SUBSTANTIAL PORTION OF THE GREASEMAKING PROCESS FOLLOWING THE SAPONFICATION STEP, SAID SHEARING BEINGCARRIED OUT BY PASSING THE RECIRCULATING MIXTURE IN SAID RECYCLE LINETHROUGH A SHEAR VALVE WITH A PRESSURE DROP ACROSS SAID VALVE OF ABOUT10-200 POUNDS PER SQUARE INCH.
 8. THE PROCESS OF CLAIM 1 WHEREIN THESAID SOAP IS A CALCIUM-HYDROXY FATTY ACID SOAP.